Answers

I have no experience (yet) because I'm working on my games, but I'm taking the opposite way you are : first Iphone and Ipod, then Ipad. Why don't release it for the two machines? The iOS license is the same! For the Mac you'll need a separate license so I guess that's really your call.

Yea you're right. I have a game called "terra god". Sales were better on iPad as well. I guess ppl other than myself, prefer the bigger screen. Either way for optimal sales, it's best to release on both